Made even funnier by the fact that the episode it is typically paired with, New Mexico, Old Monster, also had the culprit as a character that wasn't seen by the gang- or the audience!
From "A Terrifying Round With A Menacing Metallic Clown," Velma goes cowering off with Scooby (she's got a clown phobia) to the pitching cages. As she's bracing for a pitch from Scooby, she gets a slice of pizza from the pitching machine Scooby is operating. She never realized cowering off could be so much fun.
Her turning down a Scooby Snack is also hilarious:
Velma: Nice try, Daphne; I may be scared, but I'm not desperate.